Antifriction bearing and method of manufacturing the same



Patented Nov. 2, I937 ANTIFRICTION BEARING AND METHOD OF Y MANUFACTURING THE SAME Alf Gerhard Grabe', Stockholm, Sweden Ne Drawing. Application January 28, 1935, Serial No. 3,811. In Sweden January 15, 1934 9 Claims.

The ideal anti-friction metal is an alloy which consists of hard crystals embedded in a plastic ground mass. The function of the hard crystals is to lower the friction coeficient, while the softer ground mass serves to equalize possibly too high a surface pressure by the hard crystals being forced deeper into the ground mass. Ordinary anti-friction metals consists of alloys of tin, antimony, lead, and possibly, copper and other added substances. Such metals, however, possess certain disadvantages, the most important of which are a comparatively low compressive strength and acoefiicient of expansion which is considerably higher than that of the shaft if the latter made of steel, as is generally the case.

The present invention relates to a method of manufacturing machine and engine parts which have a sliding or bearing engagementwith another part, such as bearings, cylinder linings, pistons, slides or the like, of an anti-friction metal. The method according to the invention consists in making the part of a hypoeutectoid steel, that is a steel the carbon content of which a is relatively low and in any case below 0.90 per cent, heating the part to a temperature between am and 8.03, and then hardening the same in a suitable cooling medium.

A steel having a relatively low carbon-content, for instance 0.25 per cent, consists in a nonhardened condition of pearlite enveloped in a ground mass of ferrite. If this material is heated to a temperature which just exceeds the critical point am, the pearlite changes to austenite while the ferrite remains unchanged.

If from this temperature the material is hardened, the austenite changes to martensite while the ferrite remains unchanged. Through this operation a metal has thus been obtained which 40 consists of hard grains of martensite in a plastic ground mass of ferrite, and the structure of which thus corresponds to the above mentioned ideal structure, and which is therefore particularly suitable as an anti-friction metal.

The hardness of the ground mass may be varied by an addition of alloy constituents which form solid solutions with the ferrite, suchas, for instance, manganese, silicium, chrome, tungsten, and so forth. In this case it is of less importance whether such metals simultaneously are present to a certain extent in the cementite forming part of the pearlite of the non-hardened steel. Likewise the properties of the metal may be varied by employing different hardening temperatures which, however, must lie between am and aca in all cases, and finally, also by a greater or less degree of tempering. In certain cases it may also be advantageous to vary the grain size of the metal, which in such case is effected before the hardening by well-known mechanical and thermal treatments.

The advantages of manufacturing machine and engine parts which have a sliding or bearing engagement with another part, of a hypoeutectoid steel and then heat-treating the same in this manner reside primarily in the high compres-' sive strength of the steel and its power of resisting wear. Furthermore, in the case of a bearing manufactured in this manner, the coefficient of expansion of the metal of the bearing is the same as that of the shaft, for which reason the oil space remains constant also at different temperatures. In View hereof a smaller oil space is permissible, which results in less oil being consumed.

.As against a bearing made of bronze, a bearing made of an anti-friction metal according to this invention possesses the advantage that the metal is free from all abrasive constituents in which the bronze is generally rich. This is for the reason that tin oxide is often present in bronze.

Therefore, a shaft which has been running for a long time in a bronze bearing usually becomes scratched even if the bearing is protected against dust, whereas in an iron bearing made in the manner above described the shaft becomes polished and successively lowers its coefiicient of friction.

Obviously, the anti-friction metal according to this invention is suitable not only for bearings but also for other machine and engine parts which have a sliding or gliding engagement with another part, such as cylinder linings, pistons, slides, and so forth, and the term bearing used in the claims should therefore be under stood as being equivalent to such machine or engine parts. a

I claim:

1. The method of manufacturing a hearing which consists in making the bearing of a hypo" eutectoid steel, heating the same to a tempera ture between aci and ac:;, and then hardening the bearing in a suitable cooling medium.

2. The method of manufacturing a bearing which consists in making the bearing of a hypoeutectoid steel alloyed with substances which form solid solutions with ferrite, heating the bearing to a temperature between am and acs, and then hardening the same in a suitable cooling medium..

3. The method of manufacturing a bearing which consists in making the bearing of a hypoeutectoid steel, heating the bearing to a temperature between am and acs, hardening the same in a suitable cooling medium, and then tempering the steel in the bearing.

4. The method of manufacturing a bearing which consists in making the bearing of a hypoeutectoid steel alloyed with substances which form solid solutions with ferrite, heating the bearing to a temperature between an and acs, hardening the same in a suitable cooling medium, and then tempering the steel in the bearing.

5. A hearing made of a hypoeutectoid steel heated to a temperature between an and ac; and then hardened in a suitable cooling medium.

6. A bearing made of a hypoeutectoid steel alloyed with substances which form solid solutionswith ferrite and heated to a temperature begasses tween 9.01 and acs and then hardened in a suitable cooling medium.

'7. A bearing made of a hypoeutectoid steel heated to a temperature between am and ac: and then hardened in a suitable cooling medium and afterwards tempered.

8. A bearing made of a hypoeutectoid steel alloyed with substances which form solid solutions with ferrite and heated to a temperature between am and acs and then hardened in a suitable cooling medium and afterwards tempere'd.

9. An anti-friction bearing assembly comprising a bearing of hypoeutectoid steel heated to a temperature between am and ac: and then hardened in a suitable cooling medium, and a steel journal.

ALF GERI-IARD GRABE. 

